There are many conventional devices for shaping comparatively thin (e.g., less than 1/16 of an inch) sheets of metal in particular designs for metal purlins, roof panels, wall panels and many other applications. One such conventional device is a roll forming press such as seen in U.S. Pat. No. 4,903,516, which is incorporated by reference herein in its entirety. Conventional roll forming presses typically have multiple sets of rollers that are pre-positioned prior to the sheet metal blank being fed into the roll forming press. Because of the sudden introduction of extreme bending forces on the lead end of the sheet metal blank, the lead six to twelve inches of the sheet metal blank do not properly take the shape intended to be imparted by the roll forming press, although the remainder of the sheet metal blank will be properly formed. The conventional practice is simply to cut off and discard the distorted lead six to twelve inches. Normally because of the low cost and considerable length of the sheet metal blank, discarding six to twelve inches does not have a significant economic impact.
However, conventional roll forming presses become less useful when dealing with thicker and stronger metal plate, and such conventional presses have not been used to make even simple bends in steel plate with thicknesses on the order of ½ inch or larger. Also, the heavier and more expensive the metal blank, the greater the economic impact of sacrificing the lead six to twelve inches of the metal blank.
One particular application where heavy metal plates need a pre-defined bend or curvature is in the production of reinforcement plates for tanker railcars. Tanker car reinforcement plates are employed to reinforce the connection of the massive tank (which may carry 100 tons of liquid) to the wheel carriages. The reinforcement plates are typically about 23 feet long, 13 to 17 inches wide, and made of high grade ⅝ inch thick steel. The reinforcement plates will have a bend down their centerline (i.e., the side edges bending upward around the long axis of the plate) with the bend having a radius of curvature on the order of 55 to 60 inches. Because of the difficulty in imparting an accurate bend along this axis to such thick steel, the reinforcement plate is normally formed in shorter lengths, the bend imparted to those shorter lengths, and then the shorter lengths welded together to form the final 23 foot reinforcement plate. Naturally, this multi-step manufacturing process adds to the completed reinforcement plate significant costs and potential weak points at the welds.